The present invention generally relates to filter assemblies and more specifically, but not exclusively, concerns a filter with parallel fluid flow.
Filters are used in a wide variety of environments in order to filter particulate matter out of fluid. For instance, filters are used to filter particulates from both oil and fuel in engines in order to prolong the life of the engine. Conventional filter cartridge designs usually incorporate a cylindrical-shaped filter cartridge that defines a center post cavity in which a center post is received. In one typical flow pattern, the fluid is filtered by flowing through the cartridge from the outside of the cartridge to the inside of the cartridge. Usually, the fluid being filtered flows in a counter flow direction, that is the unfiltered fluid on the outside of the filter cartridge flows in one direction, while the filtered fluid in the center post cavity flows in the opposite direction. For example, when a filter cartridge with the counter flow design has a vertical orientation, the unfiltered fluid can flow in an upward direction along the outside of the filter cartridge, and the filtered fluid that is inside the center post cavity drains in a downward direction. With this counter flow filter cartridge, the pressure differential across filter media in the cartridge increases from top to bottom. For instance, the highest pressure differential is created at the bottom of the cartridge; while the lowest differential pressure is created at the top of the cartridge. The portion of the filter cartridge that has the highest pressure differential (i.e., the bottom of the filter cartridge) tends clog at a higher rate as compared to the remainder of the cartridge. As should be appreciated, this uneven pressure differential distribution allows the bottom filter media to become plugged first, such that the filter cartridge progressively clogs in an upward direction. Overt time, the effective surface area of the cartridge that can filter fluid reduces, thereby hastening the progression of clogging of the filter such that the life of the filter is rapidly reduced. Another disadvantage of the counter flow filter design, especially with fuel filters, is that the counter fluid flow disturbs the water in the filter's sump that has been already separated from the fuel such that the water and any contaminants in the water are reintroduced into the fuel. This reintroduction of water reduces fuel-water separation efficiency as well as the overall filtering efficiency of the filter cartridge.
Another problem faced with fuel filters is associated with contaminated, unfiltered fuel in the cartridge draining back into the system. Once the engine is turned off, the unfiltered fluid picks up additional contaminants from the filter media and back flushes these contaminants into the fuel system, thereby further contaminating the fuel system. Typical fuel filters require a check or ball valve in order to prevent this back flushing of contaminated fuel. However, such check valves can stick and be rendered useless if not properly maintained. Moreover, the check valves increase both the manufacturing and maintenance costs associated with the filter.
In the operation of diesel engines, fuel temperature is a critical parameter that needs to be measured. If the temperature of the diesel fuel becomes too low, the diesel fuel can become highly viscous, thereby preventing the engine from operating properly. Therefore, it has been critical to be able to monitor and control the temperature of the fuel. In typical designs, a thermostat is placed in the fuel stream in order to monitor the temperature of the fuel. A seal is generally required in order to prevent fuel leakage from the stream. Over time, this seal can deteriorate such that the seal leaks and contaminates the fuel system, which can be detrimental to engine performance.
Fuel additives are sometimes added to the fuel in order to improve the engine performance. However, over or under supply of the fuel additive can adversely affect engine performance. Controlling the supply rate of fuel additives, while critical, can be rather difficult. Typical fuel additive systems require complicated valving and other systems for controlling the supply rate of the additive.